扁平线圈钢丝绳捻距涡流响应分析及试验研究

Analysis of Eddy Current Response to Lay Length of Wire Rope with Pancake Coil and Experimental Study

捻距作为钢丝绳重要参数之一,对其进行检测可间接反映钢丝绳受力状态和表面损伤状态。针对现有图像识别方法受限于外界光照及钢丝绳表面附着物覆盖情况、漏磁法需要磁化钢丝绳等问题,提出采用双扁平线圈差分电桥的钢丝绳捻距涡流检测方法。结合Ar,V-Ar表述建立钢丝绳涡流响应分析控制方程,对单绳股涡流分布进行分析。探头正下方绳股表面涡流形成漩涡,绳股两侧曲面上涡流分布存在对称性。对扁平线圈的中径进行优化设计,当中径小于等于股间隙时,捻距检测精度高且检测灵敏度高,然后搭建试验平台进行捻距检测。试验结果与仿真均表明扫描信号中相邻波峰或者相邻波谷的间距为股间隙,一个捻距范围内扫描信号出现的波峰或者波谷数量与钢丝绳绳股数目相关。利用集合经验模态分解方法对试验结果进行后处理可以有效提取有用信号,涡流法得到钢丝绳捻距的相对误差不超过0.13%。

The lay length is one of the important parameters of the wire rope.The measurement of the lay length can indirectly reflect the stress state and the surface damage state of the wire rope.The imaging recognition method for measuring the lay length is limited by the external light and the attachment on the surface of the wire rope.The magnetic flux leakage method requires the wire rope to be magnetized.In view of the above problems,An eddy current method to detect the lay length using the double pancake coils differential bridge is proposed.Firstly,the governing formulations based on the Ar,V-Ar for the eddy current response analysis are established.Combing the formulations,the distribution of the eddy current in the single strand is simulated.It forms vortex on the strand surface just under the pancake coil.The distributions of the eddy current on the curved surfaces of the two sides of the strand are symmetrical.Secondly,the medium radius of the pancake coil is optimized.When the medium radius equals to or is smaller than the gap between the two adjacent strands,the detection precision of the lay length is high and the detection sensitivity is also high.Thirdly,the experimental platform is set up to test the lay length.The experimental results and the simulation results show that the distance of the adjacent peaks or throughs of the scanning signal is just the gap between the two adjacent strands.The number of the peaks or throughs of the scanning signal in the lay length is related to the strands number of the wire rope.Finally,in order to effectively extract the useful information from the experimental results,the ensemble empirical mode decomposition(EEMD)method is utilized.The results show that the relative error of the wire rope lay length obtained by this method is less than 0.13%.